Rice Cooker Eco-Hack
 

Rice cookers work great, I really like them. I most often have some form of cooked brown rice for breakfast. Load it up with fruit and nuts and a wee touch of molassas and you're talking about quality living.

But look at the bottom plate to see how much power it uses.

Mine said 400 watts.

This should be better.

So I opened it up to have a look inside.


First off, there's no insulation, not any.

Second off, I measured the cooker's wattage when it was off and was reading... It was drawing 385 watts before I turned it on!

So the way the circuit works is that the "warm" functions when ever the cooker is plugged in. The warming temp switch senses when an over temp situation happens (something above 212 F) and switches off. When the unit cools, the switch goes back on, etc. This power cycling keeps the rice warm and gobbles up huge watts.

So the most obvious hack is to disable the warm circuit.

The second is to add insulation.

The third is to insert an in-line diode to turn it into a half-wave device, drawing power only for half a wave, thus reducing power by half.


(to be continued)

Oooh, interesting.

I can understand the insulation and warm kill hack. Why do you want to reduce the power by half though?

The diode in series is said to save energy. Something about the asymmetry allowing you to get more power for your money. I'm planning to modify a radiator heater with some SCRs to do the same and silence it at the same time. (It currently uses relays to control heat, which means that if I use it as a bedroom heater, I would have to put it farther away, reducing efficiency. The SCRs will do the half wave trick and not make any noise when switching.)

I have read about various approaches to high efficiency cooking, and the low efficiency of normal stoves is always pointed out. most of the heat under a pot is lost as it passes around the pot.

I've also read about "Fireless Cooking" which actually uses fire to initially get the food hot, but then uses thick insulation to keep the heat in the pot, where the cooking continues for hours.

So I reasoned that the insulation would prevent the loss of heat through the sides of the cooker... therefore, less heat would be required.

Turns out that the diode works just about right. However, the rice cooks just a bit slower.

Regards,

-AC_Hacker

Sounds like how Frank Lee from EcoModder.com cooks pasta. See point number 3 in this post.

AC, that trick with the diode is neat, first I've heard. Can't find any info on it, though. What kind of diode did you use?

I've seen cheap lamps that use a switch that will select 'diode' or 'direct' to give you 'low light' or 'full light'.

I searched through my parts box looking for one with 2x the amp rating (> 7 amps) and 2x the volt rating (> 220 volt), couldn't find it, so I settled for a 100 volt, 5 amp diode. So far, it's working...

Regards,

-AC_Hacker

That's pretty trick... I don't use a rice cooker, though. I used to always just do it on the stove, then keep the partially cooked rice soaked in cold water in the fridge, and heat it up in the nuker for about 2 minutes (for a big bowl, 1200W microwave), which would have it cooked perfectly to my taste. Add some dairy or goat's milk, and a little sugar, and consume. Enough calories for a half day's work, for sure, and great tasting as well.

Soaking Hack...
 

Your post reminds me of the practice of soaking dry beans overnight before cooking them.

I suppose the same could be done to rice.

It could turn out that just soaking the rice could save more energy than anything I have tried.

Sometimes I feel like I'm re-inventing the past.

Regards,

-AC_Hacker

LOL

I took a survival course at one point... and par normal, we were allowed to take (1) food item with us, along with essentials, like a knife, some cloth, extra clothes, etc (things you should have when hiking alone anyway).

My food item was rice, because it has such a high carb content, and it was winter, with snow on the ground.

Clear plastic rice bowl, dumped out some of the rice that I took into the cloth to save for later, put stream water in the bowl, put the lid back on, and let it sit in the sun all day. By the time it started really getting cold out, I had a fairly warm bowl of rice to enjoy while starting the fire so I could heat up my rabbit. :)

Those were the days, eh?

Have you measured total energy usage with and without the modifications? That would be very interesting to see.

Also, how did you disable the warming feature?

Daox,

You're reading my tattered mind.

I just got back from the store with enough rice to do the trick.

It all means that I'll have to undo the hacks... but anything for science.

Stay tuned...

-AC_Hacker

Any updates here? :)

updates...
 

Well, I'm limited by how fast I can eat rice.

But seriously, I wanted to get my datalogger going but I had misplaced the power sensor box I built. Finally found it, and now the batteries in the datalogger don't seem to be holding a charge so well. I'm gonna try to cobble together an AC source with a battery backup.

In the meantime I'm using my kill-a-watt (which continues to really rock), and my post-hack data is running like so:

cooking power = 193 watts (with diode)
cooking time = 1 hour, 24 minutes
cooking kW-h = 0.27 kW-h

Regards,

-AC_Hacker

Updates? I'm quite interested to see if this reduced energy consumption noticeably.

does this have a timer or something to turn it off? if it doesn't then I would add a bath fan timer switch, when I cook rice on the stove top I tend to turn it off about 15 minutes before it's done and let it finish cooking as it slowly cools down, I never burn rice this way and it's always perfect.

When I cook rice on the stove I often forget about it, until the water evaporates and it starts to burn... :(

For central Europe - a potato cooker, that's what I'd like to see ;) Dad-in-law just lives on 'taters...

I have left the original mechanism in place for now.

The principle of operation is based on behavior of certain materials that posess magnetic properties. When they are heated, their magnetic property is essentially unchanged until a critical temperature is reached. At that critical temperature, the magnetic property is suddenly lost completely. When the material cools back down below the critical temperature, the magnetic property returns completely.

In a rice cooker, the magnetic material is affixed to a spring-loaded arm that presses a microswitch. When the rice cooking pot is in the cooker and the rice cooker is turned on, the spring loaded arm is brought up until the magnet material sticks to a small steel disk. When the rice is cooking, the temp goes to 212 degrees F, but doesn't go over. When the free liquid water is taken up through absorption by the rice and through boiling off, the temp goes up enough that the magnetic material loses its magnetic property, the spring loaded arm drops, and the microswitch opens, which cuts power to the cooker.

Pretty clever switch, safe and very reliable.

I have so far completed one logged test cycle, with un-soaked rice, with the diode and insulation in place.

Here is a graph of that data:


I haven't scaled the data, but there's still something here to learn...

Green line is power. minimum value = 0 watts, maximum value = 193 watts

Red line is cooking temperature (probe was about in the center of the cooking area). minimum value = 64 degrees F, maximum value = 212 degrees F.

Blue line is ambient temperature. Center value is 70 degrees F.

Regards,

-AC_Hacker

Rice Cookin' (part 2)...
 

Here is the data plot for hacked rice cooker using rice that had been soaked overnight:


It was my assumption that soaking the rice overnight would greatly reduce cooking time. As can be seen from the graphs, the cooking time is reduced, but not greatly. I'm measuring cooking time by the time the power is on. But even with the power cut, the rice will continue to cook for a long time, since it is insulated. Note the long temperature decline curve.

Regards,

-AC_Hacker

I noticed that the red line (temperature) 'dips' 2 or 3 times in the soaked graph. What could that be?

My theory with soaking overnight is that by morning the rice and water are at room temperature, while if you start with dry rice and pour water in just before cooking, the water will be cooler than room temperature. This means you need slightly more energy to warm the water to room temperature.

Good point Piwoslaw.

Very interesting test results AC Hacker. I too would have thought that soaking would have made a much bigger difference.

I wonder... could it be possible to hack a coffee maker in a similar fashion? a "normal" coffee maker can consume 900-1000w while its in initial warmup (then levels off to an average of about 150-200w between heating element on and off time). Also, insulating a glass carafe would be interesting.

Coffee Maker Eco-Hack...
 

My thinking when I did the hack was that if I could prevent heat from radiating away, that I could reduce the amount of energy needed to cook the rice.

The rice cooker is already designed with a heating element of the properr wattage that will provide a medium simmer. The simmer will continue until enough water has been boiled off that it will no longer limit the temperature in the pot to 212 degrees. Then, when the temperature rises, te power is cut. So there is a time-temperature limit built into the design.

I figured if I insulated the pot well, it would retain heat and I could reduce the power by half with a diode, the 212 temperature level would still be reached and cooking would happen with a lower power. It worled out that way, but the cooking time takes a bit longer.

It will be interesting to see what you come up with regarding your coffee pot hack.

BTW, I think that thermally insulated carafs are already included in some coffee makers.

Regards,

-AC_Hacker

Have you figured out how much energy your hack has saved?

Great question.

I haven't yet. I'll need to pull out the insulation and jump past the diode.

It needs to be done.

-AC_Hacker

Some coffee makers come with stainless steel carafes that have fiberglass or other insulation in them. Some also, apparently, are vacuum sealed canteen style carafes.

When the glass one broke on my Father's coffee pot, I stuck a metal coffee can with a bend in the lip under the dripper. Worked fine until he got a new coffee maker for Christmas from a relative.

Bumping this because I wanna know if it worked. :)

Revisiting the Rice Cooker Eco-Hack...
 

I noticed that the rice was well-cooked after the eco-hack, maybe too well...

As previously explained, the mechanism of timing the rice cooker's cook cycle relies on boiling off the cooking water. When the water has been absorbed by the rice and the rest boiled off, the temperature rises and the cycle is ended.

For brown rice, the normal water-to-rice ratio is about 2.5 to 1.

The Eco-Hack added insulation which reduced heat loss, and it reduced the power being used by half by using a diode. After this has been done, the time for the cooker to reach cooking temperature is longer than an unmodified cooker. Once the temperature is reached, the cooker simmers the rice & water at a slightly less vigorous level, but 212F is still 212F.

So, cooking took longer, and the rice was over-cooked, not burned, but too soft almost mushy.

Finally, it dawned on me that I could reduce the cooking time by reducing the amount of water being used. After several trials, I settled on a water-to-rice ratio of about 1.8 to 1.

So, to summarize, an unmodified cooker uses enough power to cause the absorbtion and boiling off of 2.5 cups of water per cup of rice. While a modified cooker uses enough power to cause the absorbtion and boiling off of 1.8 cups of water per cup of rice. This would imply a reduction in power used by at least 30%. And, since I have not yet tried a before and after power reading, the actual efficiency due to the retaining of heat by the insulation will surely be higher.

If you look at this post, in the second photo you will see a pointer bearing the labeled "remove warm wire". When you remove that wire, put heat shrink tube over the wire and tuck it out of harm's and heat's way. That's all it takes.

Regards,

-AC_Hacker

Interesting experiment you have going there, I use a slow cooker often enough to think about modding it, however one thing they have in common is the closed air gap surrounding the heated bits, an air gap in its self is a good insulator, packing this area with fiberglass will stop air convection currents?, you could equally leave out the insulation and stick some shiny foil to the inside of the outer bowl, to reflect the heat back inside.

Cheers
Mike

Slow Cooker...
 

This could work, I don't know if it would work better than insulation or if the cooker would work better with a radiant barrier inside the heated area AND insulation outside the heated area.

One thing that fascinates me about the rice cooker is the clever magnetic switch. It's not only a convenience feature but also a safety feature.

I don't think that magnetic switches are used in slow cookers... you don't have the same cooking conditions as when cooking rice.

But using fireproof insulation in a slow cooker would improve efficiency. The diode trick might work in this case, also a high-power dimmer switch would do it too, as would a short-burst cooking cycle combined with very good insulation, which would allow the food to continue cooking long after the power was removed.

...more here...

...and still more here...


Roll up your sleeves my friend, there's efficiency to be found!

Best Regards,

-AC_Hacker

How long does it take to cook, and how much is cooked? I can do a little over four cups of rice in a microwave rice pot in 18 minutes @ 1,000 watts, or about 300Wh.

comparing apples to apples...
 

I don't think that my cooker will hold that much.

From your brief description, I suspect you're cooking white rice.

Tell you what, Why don't you cook up 2 cups of brown short grain rice and let me know what kind of cooking time you come up with.

Don't know if you've cooked brown rice before, but it cooks differently than white rice.

Here's a recipe I found:


Cooking Directions - Brown Rice In the Microwave

1. Combine 1 cup brown rice, 3 cups water in a 2 ½ quart microwave-safe dish. ( I suggest microwave glassware, see below) Microwave UNCOVERED on HIGH for 10 minutes.
   
2. REDUCE power to 50%, microwave uncovered 20 minutes. After the Brown rice is completely cooked, allow it to sit for 5 minutes.

Let me know what your results are...

I'll do the same.

Regards,

-AC_Hacker

Sorry, didn't realize you're cooking brown rice; we usually cook Basmati. If the above recipe actually works, it would be about 20 minutes total cook time (about 333Wh) plus 10 minutes of running just the turntable, light and fan. (I'll hook up the Kill-a-Watt and see how much juice it pulls running just those.)

The Great Rice Race...
 

Perhaps a moment of perspective is in order here...

The amounts of energy we're talking about here are very small. in fact we're probably talking about an advantage of one method over another, that in terms of money is worth less than a penny.

But in terms of a percentage of energy consumed, it is worth taking note of, because what we learn could apply to another instance where the power is significant.

As an actual exercise, where two people took action and did a physical experiment, it is really pretty valuable. It is good that you actually put a kill-a-watt on your microwave and actually know that it draws 1000 watts when it runs. My microwave is rated at 1500 watts, but when I measured it with the kill-a-watt, it measures 1376 watts. I trust my kill-a-watt.

I know that when I cook white rice in a pot on top of the stove, it takes 20 minutes, and when I cook brown rice on top of the stove, it takes at least 45 minutes, which is over 100% different, and not to be overlooked. So it's also good that you have actually cooked the brown rice to see that the recipe really works in your microwave, so that you know your measured power is actually valid.

So my cook time was about 71 minutes... the rice cooker shut off when I wasn't looking, so the time is approximate.

But what we're really after is power, and the actual power consumed during cooking was 260 watts, data captured by the kill-a-watt.

BTW, I measured the amount of water volumetrically, and verified it with a digital scale. The amount of rice was carefully measured by volume, Using the same cup I used for the water.


Regards,

-AC_Hacker

Lower Max cooking temperature?
 

I would like to try this hack with a cheap rice cooker. But this rice cookers cooking temperature and "keep warm" temperature are too hot. The rice cooks in 15-20 minutes and the keep warm setting starts burning the rice after about 15 minutes. Any input from you pros how I could go about lowering the default cooking temperature a bit in addition this hack?